1. Field of the Invention
The invention generally relates to cartridges for magnetic disks on which information may be recorded in concentric or spiral tracks. More particularly, the invention relates to an improved cartridge for protecting one or more recording surfaces on the disk from dust and other contaminants.
2. Description of the Prior Art
Magnetic disks have been used for a number of years to record information in various types of devices, such as word processors and computer systems. Typically, such disks, sometimes referred to as "floppy disks" because of their lack of stiffness, are housed in a cartridge to prevent the flexible disk from being folded or otherwise seriously damaged and to protect the sensitive magnetic surface(s) of the disk from dust, fingerprints, and other contaminants. The perspiration or grease left by fingerprints on a magnetic surface of the disk will reduce the amplitude of the information signals, recorded on or read from the magnetic surface, by providing an intervening medium between the disk surface and the magnetic head. Dust and other airborne debris settling on the magnetic surface can cause surface scratches and will hasten wear of the magnetic head. All of this, of course, reduces the effectiveness and the life of the disk and the head.
Many of the disk cartridges that are generally available have at least one access opening through which a magnetic head can be received to record or read information on a magnetic surface of the disk. When using such a cartridge, however, dust as well as fingerprints can reach the magnetic surface through the access opening. To prevent this from happening, a shutter or a cover door is usually included, such as shown in U.S. Pat. Nos. 4,120,012 and 4,188,650. The cover door is normally positioned across the access opening to close the opening, but can be retracted from the opening to permit head access to the magnetic surface.
While cover doors, such as those shown in the '012 and '650 patents, provide some measure of protection for a magnetic surface of the disk in the vicinity of an access opening in the cartridge, they do not appear to provide sufficient protection from dust and other granular contaminants, which can enter through other openings in the cartridge or atop the cover door as it is opened. For example, dust may enter one or more central openings in the cartridge for receiving a drive spindle to rotate the disk. Since the cover door is spaced from a magnetic surface of the disk and does not enclose the disk, the dust will likely flow onto the magnetic surface.